The present invention relates generally to systems for electronically controlling and managing the operation of internal combustion engines, and more specifically to such systems for controlling engine operation during gear shifting operations.
Electronic control systems for managing the operation of internal combustion engines are well known and widely used in the automotive and tractor truck industries. Such systems are typically operable to control engine fueling as well as many other engine and/or vehicle operating conditions.
Designers of electronic engine control systems have heretofore devised numerous techniques for controlling engine fueling during various engine operating conditions, and one such technique is illustrated in FIG. 1. Referring to FIG. 1, a prior art technique for controlling engine fueling to thereby limit engine speed during manual gear shifting operations is illustrated, wherein such a technique is commonly referred to as progressive shift control. FIG. 1 shows a graph of engine RPM vs. vehicle speed, wherein a linear engine speed limit 10 is typically established by specifying a first engine speed limit RPM1 at a first vehicle speed VS1 and a second engine speed limit RPM2 at a second vehicle speed VS2. The engine speed limit 10 linearly increases from RPM1 to RPM2 between VS1 and VS2 and is held constant at RPM2 beyond VS2, wherein RPM2 is typically less than rated engine speed 12. Rated engine speed, also known as governed engine speed, is defined for purposes of the present invention as the engine speed at which the engine produces an advertised engine output horsepower or torque value.
The purpose of progressive shift control is to gradually increase available engine speed (and thus more engine power) as vehicle speed increases between VS1 and VS2, wherein typical values for VS1 and VS2 are 0.0 and 40 mph respectively. This engine speed limiting scheme accordingly encourages the vehicle operator to manually shift gears at lower engine speeds than may otherwise occur, particularly in the lower transmission gears, thereby resulting in fuel savings associated with more efficient engine operation. This feature is illustrated by gear shifting pattern 14 wherein three gear shifts are shown, each occurring at progressively increasing engine speed values.
While the progressive shift control feature 14 illustrated in FIG. 1 achieves the goal of encouraging vehicle operators to shift at lower engine speeds, it has certain drawbacks associated therewith. For example, under high engine load operating conditions, such as when traversing a grade and/or when hauling a heavily loaded trailer, providing a hard limit 10 on available engine speed can hinder the drivability of the vehicle. One example of such hindered drivability is shown by shifting pattern 16 of FIG. 1, which illustrates the effect on the shifting pattern 14 of a steep grade encountered by the same vehicle. Under such operating conditions, the limit 10 on engine speed causes the vehicle operator to shift sooner than would otherwise be preferred and the effect of the steep grade causes additional loss in both engine speed and vehicle speed over that of shifting pattern 14. Under severe operating conditions, the vehicle may accordingly have insufficient momentum to justify a shift to the next higher gear, thereby defeating the purpose of engine speed limit 10. What is needed under such conditions, is the ability to increase engine speed up to rated engine speed 12 before shifting to the next higher gear as illustrated by shifting pattern 18 in FIG. 1, wherein engine speed following a shift should ideally remain above a peak torque engine RPM 15. This scenario would improve grade climbing performance as well as the likelihood of successfully completing the shift, wherein both of these improvements result from additional kinetic energy present in the vehicle prior to the shift and from the increased engine power and response after the shift. However, while sufficient engine speed for grade climbing and the like is necessary, there is also a need for limiting engine output conditions during such grade climbing or other operation so as to maintain fuel efficient engine operation.
What is therefore needed is a system for controlling engine operation to thereby achieve desired fuel economy goals while also allowing for additional engine output only when the need therefore legitimately exists.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for controlling an internal combustion engine comprises a memory having stored therein an engine output characteristics map for an internal combustion engine, and means for establishing a region of the engine output characteristics map wherein engine operation is undesirable, wherein the region defines a first border as a function of engine speed and a second border intersecting the first border.
In accordance with another aspect of the present invention, a method of engine control comprises the steps of establishing in memory an engine output characteristics map for an internal combustion engine, establishing in memory a first border relative to the engine output characteristics map as a function of engine speed, and establishing in memory a second border relative to the engine output characteristics map and intersecting the first border, wherein the first and second borders define a region of the engine output characteristics map wherein engine operation is undesirable.
In accordance with yet another aspect of the present invention, a system for controlling an internal combustion engine comprises a memory having stored therein an engine output characteristics map and a region thereof of undesirable engine operation, wherein the region has a first border defined as a function of engine speed and a second border intersecting the first border, and a control computer controlling engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside of the region.
In accordance with still another aspect of the present invention, a method of engine control comprises the steps of providing in memory an engine output characteristics map for an internal combustion engine, providing in memory a region of the engine output characteristics map of undesirable engine operation, wherein the region has a first border defined as a function of engine speed and a second border intersecting the first border, and controlling engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside the region.
In accordance with a further aspect of the present invention, a system for controlling an internal combustion engine comprises a memory having stored therein an engine output characteristics map of an internal combustion engine and a region thereof of undesirable engine operation, means for producing an engine output control override indicator, and a control computer executing a first engine output control strategy for control engine operation according to the engine output characteristics map while maintaining or encouraging engine operation outside the region as long as said engine output control override indicator is inactive. The control computer is otherwise operable to execute a second engine output control strategy for allowing engine operation anywhere within or on said engine output characteristics map.
One object of the present invention is to provide a system for controlling engine operation to thereby maximize fuel economy during shifting while allowing for increased engine performance when a need therefore legitimately exists.
Another object of the present invention is to provide such a system operable to control engine output conditions particularly during shifting to thereby achieve the aforementioned goals.
A further object of the present invention is to provide such a system operable to control such engine output conditions by controlling at least one of engine speed, engine acceleration and engine fueling rate.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiments.